The present invention relates to a new and improved method of, and apparatus for, determining the starting point and the end point of a spatial closed signal pattern in a time sequence of individual ones of such spatial closed signal patterns, each of which is constituted by a series of measuring signals.
Spatial closed signal patterns of the aforementioned type may constitute, for example, physiological measuring signals which are picked up from a living being by means of electrodes and such spatial closed signal patterns occur, for example, in the as-such known methods of vector cardiography. Such a method is described in detail in European Patent Publication No. 0,086,429 and the aforementioned cognate U.S. Application Ser. No. 06/464,765. In this method as well as in other known methods of vector cardiography the starting points and the end points, for example, of the P-, QRS- and T-loops or waves are visually determined by the physician who must interpret the curves presented to him or her. This is evident, for example, from "Computers in Cardiology", 1982, IEEE, page 429 et seq. entitled "Automated Vector Cardiographic Analysis by an Inexpensive Microprocessor" (ISBN No. 0-8186-0024-1). It also follows therefrom that the determination of the starting points and of the end points by computation using an electronic computer tends to yield still less reliable results than the simple visual determination.
A further possibility for determining the starting point and the end point of a signal pattern as produced in the known vector cardiogram comprises the steps of selecting sections from a present signal pattern in which the signal does not or nearly does not change with time. An electrical starting, end, or base potential can be attributed to such sections which indicates that the starting point and the end point of the signal pattern are located in the region of such sections. However, when such a procedure is used, the definition of the starting point and of the end point is still indefinite with respect to time.
The determination of the starting point and the end point of a signal pattern is particularly difficult when the signal pattern has superimposed thereon oscillations of a very low frequency. In a vector cardiogram, for example, such an oscillation is effected by the breathing of the investigated person or patient. When the vector cardiogram is recorded under circulatory stress, such oscillations distort the signal pattern to such a degree that the determination of the starting point and the end point with sufficient reliability by means of the hitherto known methods is impossible.